Module: ASTTransform::Testing::Assertions

Defined in:
lib/ast_transform/testing/assertions.rb

Overview

Assertions for transform authors' own test suites — the enforcement arm of the authoring contract ("textual order is source order"). Minitest-flavored. Never loaded in production; require it from test code:

require "ast_transform/testing/assertions"

class MyTransformationTest < Minitest::Test
include ASTTransform::Testing::Assertions
end

Instance Method Summary collapse

Instance Method Details

#assert_backtrace_lines(source, path:, raise_at:) ⇒ void

This method returns an undefined value.

Runtime complement of assert_line_aligned: compiles source through the full pipeline under path, executes it, and asserts the raw first backtrace frame — no filtering of any kind — is ":<raise_at>".

Parameters:

  • source (String) —

    fixture that raises when executed

  • path (String) —

    pseudo source path to compile under

  • raise_at (Integer) —

    expected source line of the raise



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# File 'lib/ast_transform/testing/assertions.rb', line 56

def assert_backtrace_lines(source, path:, raise_at:)
  iseq = InstructionSequence.source_to_transformed_iseq(source, path)

  error = assert_raises(StandardError, "fixture at #{path} should raise when executed") do
    iseq.eval
  end

  location = error.backtrace_locations.first
  assert_equal "#{location.path}:#{raise_at}", "#{location.path}:#{location.lineno}",
    "raw backtrace should cite source line #{raise_at} of #{path}"
end

#assert_line_aligned(source, *transformations, path: 'fixture.rb') ⇒ void

This method returns an undefined value.

Transforms source through the real pipeline (transform + line-aligned emission), re-parses both sides, matches surviving statements by location, and asserts each one's emitted line equals its source line. Statements the transform deletes (e.g. description strings) are exempt; statements the transform rewrites in place keep their anchor and are checked.

Parameters:

  • source (String) —

    fixture source

  • transformations (Array<ASTTransform::AbstractTransformation>)
  • path (String) (defaults to: 'fixture.rb') —

    pseudo-path used for parsing and messages



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# File 'lib/ast_transform/testing/assertions.rb', line 26

def assert_line_aligned(source, *transformations, path: 'fixture.rb')
  transformer = Transformer.new(*transformations)
  emitted = transformer.transform_file_source(source, path, path)

  source_lines_by_statement = statement_lines(transformer.build_ast(source, file_path: path))
  emitted_lines_by_statement = statement_lines(transformer.build_ast(emitted, file_path: path))

  misaligned = source_lines_by_statement.filter_map do |render, source_line|
    emitted_line = emitted_lines_by_statement[render]
    next if emitted_line.nil? || emitted_line == source_line

    format('  MISALIGNED %s: source line %d, emitted line %d', render, source_line, emitted_line)
  end

  assert misaligned.empty?, <<~MESSAGE
    expected every surviving statement at its source line in #{path}:
    #{misaligned.join("\n")}

    emitted:
    #{numbered_listing(emitted)}
  MESSAGE
end